Abstract: When fuel-rich explosives are detonated in a confined space, their load characteristics are verified to exhibit remarkable differences from those generated in an open space. Specifically, the reflected shock waves are significantly intensified, the afterburning effect is prominently manifested, and the effective duration during which the expansion of detonation products performs work is obviously prolonged. Meanwhile, the calculation of structural deformation under the action of confined blast loading is confronted with multiple challenges, including a large number of involved variables, complex expression forms and high research costs. To tackle these problems, based on a validated numerical calculation method for explosion loads in confined spaces where the afterburning effect is taken into consideration, a systematic analysis is carried out on the spatiotemporal distribution law of explosion loads in confined spaces, and an equivalent load simplification method that simultaneously accounts for the saturation response time and quasi-static pressure is proposed in this paper. Through an in-depth investigation into the spatial distribution form of the equivalent load and the influence exerted by quasi-static pressure on structural response, the results demonstrate that within the scope of the current research, the impact of the spatial distribution of the equivalent load on structural response is relatively minor, whereas the contribution of quasi-static pressure cannot be neglected. On the basis of the above research findings, a two-stage load simplification model represented by the load characteristics at the central point of the target plate is further developed. A comparative analysis is conducted between the residual deformation values derived from 10 groups of simplified models and those obtained from actual experiments, which verifies the effectiveness of the established simplified model. The research results indicate that the proposed model possesses excellent applicability under different working conditions, can not only guarantee calculation precision but also remarkably enhance computational efficiency, and thus provides a reliable technical approach for the simplified analysis of engineering problems related to confined space explosions.